Tip - SonicWALL NSA 240 Getting Started Manual

Configuring HA
The first task in setting up HA after initial setup is configuring
the High Availability > Settings page on the Primary
SonicWALL security appliance. Once you configure HA on the
Primary SonicWALL security appliance, it communicates the
settings to the Backup SonicWALL security appliance.
To configure HA on the Primary SonicWALL, perform the
following steps:
1. Navigate to the High Availability > Settings page.
2. Select the Enable High Availability checkbox.
3. Under SonicWALL Address Settings, type in the serial
number for the Backup SonicWALL appliance.
You can find the serial number on the back of the SonicWALL
security appliance, or in the System > Status screen of the
backup unit. The serial number for the Primary SonicWALL is
automatically populated.
4. Click Apply to retain these settings.
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Configuring Advanced High Availability Settings
1. Navigate to the High Availability > Advanced page.
2. To configure Stateful HA, select Enable Stateful
Synchronization. A dialog box is displayed with
recommended settings for the Heartbeat Interval and
Probe Interval fields. The settings it shows are minimum
recommended values. Lower values may cause
unnecessary failovers, especially when the SonicWALL is
under a heavy load. You can use higher values if your
SonicWALL handles a lot of network traffic. Click OK.

Tip:

Preempt mode is recommended to be disabled after
enabling Stateful Synchronization. This is because
preempt mode can be over-aggressive about failing
over to the backup appliance.
3. To backup the firmware and settings when you upgrade the
firmware version, select Generate/Overwrite Backup
Firmware and Settings When Upgrading Firmware.
4. Select the Enable Virtual MAC checkbox. Virtual MAC
allows the Primary and Backup appliances to share a
single MAC address. This greatly simplifies the process of
updating network ARP tables and caches when a failover
occurs. Only the WAN switch to which the two appliances
are connected to needs to be notified. All outside devices
will continue to route to the single shared MAC address.